The prior art is replete with variations on fifth wheel assemblies for coupling a towed trailer to a towing tractor. The variety of units share a locking assembly carried by the tractor to engage a depending king pin carried by the trailer. The locking assembly relied on in the past has included a resiliently loaded jaw member which closes about the king pin to secure it against a fixed seat in the fifth wheel. In some instances, a wedge has been used to hold the jaw in cooperative locking relationship. Resilient members have been biased to urge the components into cooperative relationship. When the king pin is to be released from the fifth wheel, it is sometimes necessary to apply extraordinary force to disengage the components. Even when the components are not "frozen" by accumulated grit or excessive force applied in locking the apparatus, in excess of 120 pounds of force is often necessary to open the fifth wheel, therefore, a degree of physical prowess is required to operate the device. Exemplary of the prior art in this field are the following U.S. Pat. Nos. 2,371,750; 3,318,616; 3,630,545; 3,844,854; and, 4,140,328.
Despite the numerous patents on fifth wheel technology, there remains a need for a fifth wheel which securely locks the kingpin such that "squirting", i.e. inadvertent disengagement, is avoided, yet which can be opened without excessive force.